Manufacture methods and apparatus for turbine engine acoustic panels

ABSTRACT

An acoustic panel for a gas turbine engine, includes a panel body, a panel-body cover, and a support bracket. The panel body is configured to dampen vibrations caused by the gas turbine engine. The forward support bracket is configured to mount the acoustic panel to portions of the gas turbine engine.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Embodiments of the present disclosure were made with government supportunder Contract No. FA8650-19-F-2078. The government may have certainrights.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to gas turbine engines, andmore specifically to acoustic panels for gas turbine engines.

BACKGROUND

Gas turbine engines used in aircraft often include a fan assembly thatis driven by an engine core to push air through the engine and providethrust for the aircraft. A typical fan assembly includes a fan rotorhaving blades and a fan case that extends around the blades of the fanrotor. During operation, the fan blades of the fan rotor are rotated topush air through the engine. The fan case both guides the air pushed bythe fan blades and provides a protective band that blocks fan bladesfrom escaping the fan assembly in case of a blade-off event in which afan blade is released from the fan rotor.

Fan cases sometimes include acoustic panels positioned near or adjacentto the rotating blades of the fan assembly. Acoustic panels aregenerally used to dampen noise and vibrations produced by the rotatingblades during operation of the gas turbine engine. Acoustic panels maybe challenging components to design with secure attachment and supportbut also to maximize treatment (i.e. noise dampening) area whileminimizing weight and cost. Poorly secured acoustic panels mayexperience movement in operation which could cause fretting and wearagainst the case. Some attachment schemes may reduce noise attenuationand flutter margin by decreasing effective area while others mayincrease the weight of the acoustic panel with a number of bolts andfillers. Accordingly, methods and apparatuses for mounting and formingacoustic panels for fan rotors remains an area of interest.

SUMMARY

The present disclosure may comprise one or more of the followingfeatures and combinations thereof.

According to one aspect of the present disclosure, an acoustic panel fora gas turbine engine includes a panel body, a panel-body cover and aforward support bracket. The panel body includes an outer body sectionhaving a first axial length and an inner body section having a secondaxial length greater than the first axial length. The panel-body coverincludes a radially outer skin coupled to the outer body section of thepanel body and a radially inner skin coupled to the inner body sectionof the panel body. The forward support bracket is coupled to the panelbody and is arranged radially between the radially outer skin and theradially inner skin. The forward support bracket includes an attachmentflange that extends axially forward away from the outer body section anda panel-body support coupled to the inner body section of the panel bodyand at least partially spaced apart from the attachment flange toprovide a radial cavity between the attachment flange and the panel-bodysupport.

In some embodiments, the panel-body support includes an outerradially-extending strip coupled to the outer body section and theattachment flange, an outer axially-extending strip coupled to the innerbody section, an inner radially-extending strip coupled to the innerbody section.

In some embodiments, the panel-body support further includes an inneraxially-extending strip located radially between the inner body sectionand the radially inner skin.

In some embodiments, the inner body section is formed to include acutout and the inner axially-extending strip is located in the cutout.

In some embodiments, the radial cavity is defined by the attachmentflange, the outer axially-extending strip and the outerradially-extending strip, and wherein the radial cavity opens axiallyaway from the panel body.

In some embodiments, the attachment flange includes an outeraxially-extending strip coupled to the radially outer skin and aradially-extending strip coupled to at least one of the inner bodysection and the panel-body support.

In some embodiments, the attachment flange is made from a firstglass-reinforced polymer material and the panel-body support is madefrom a second glass-reinforced polymer material different than the firstglass-reinforced polymer material.

In some embodiments, the attachment flange further includes an inneraxially extending strip spaced radially from the outer axially-extendingstrip and that is coupled to the panel-body support and partiallydefines the cavity radially between the outer axially-extending stripand the inner axially-extending strip.

In some embodiments, the panel body includes an aluminum honeycombmaterial, and wherein the radially outer skin, the radially inner skin,and the forward support bracket each include a glass-reinforced polymer.

In some embodiments, the forward support bracket is bonded to theradially outer skin by a first supported adhesive layer and forwardsupport bracket is bonded to the radially inner skin by a secondsupported adhesive such that loads are transferred from the radiallyinner skin, through forward support bracket, and to the radially outerskin.

In some embodiments, a layer of unsupported adhesive is arranged to liebetween the panel core and the radially outer skin and between the panelcore and the radially inner skin.

In some embodiments, a layer of foamed adhesive is arranged to lieaxially between the panel core and the forward support bracket.

In some embodiments, the acoustic panel further includes an aft supportbracket coupled to an aft end of the panel core and arranged to lieradially between the radially outer skin and the radially inner skin,the aft support bracket defines a second cavity radially between theradially outer skin and the radially inner skin and located axially aftof the panel core.

According to another aspect of the present disclosure, an acoustic panelfor a gas turbine engine includes a panel body including an outer bodysection and an inner body section, and a support bracket coupled to thepanel body. The support bracket includes an attachment flange thatextends axially forward away from the outer body section and apanel-body support coupled to the inner body section of the panel bodyand at least partially spaced apart from the attachment flange toprovide a radial cavity located between the attachment flange and thepanel-body support and located radially outward of the inner bodysection.

In some embodiments, the acoustic panel further includes a panel-bodycover including a radially outer skin coupled to the outer body sectionof the panel body and a radially inner skin coupled to the inner bodysection of the panel body to locate the support bracket radially betweenthe radially outer skin and the radially inner skin.

In some embodiments, the panel-body support includes an outerradially-extending strip coupled to the outer body section and theattachment flange, an outer axially-extending strip coupled to the innerbody section, and an inner radially-extending strip coupled to the innerbody section.

In some embodiments, the panel-body support further includes an inneraxially-extending strip coupled to a radially inner surface of the innerbody section.

In some embodiments, the attachment flange includes an outeraxially-extending strip and a radially-extending strip coupled to atleast one of the inner body section and the panel-body support.

In some embodiments, the attachment flange further includes an inneraxially extending strip spaced radially from the outer axially-extendingstrip and that is coupled to the panel-body support and partiallydefines the cavity radially between the outer axially-extending stripand the inner axially-extending strip.

In some embodiments, the panel body includes an aluminum honeycombmaterial, and wherein the support bracket includes a glass-reinforcedpolymer, and wherein a layer of foamed adhesive is arranged to lieaxially between the panel core and the support bracket.

These and other features of the present disclosure will become moreapparent from the following description of the illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cutaway view of a gas turbine engine that includes a fan, acompressor, a combustor, and a turbine, the fan including a fan rotorhaving a plurality of fan blades configured to rotate about an axis ofthe engine and a fan case assembly that surrounds the fan bladesincluded in the fan rotor and showing that the fan case assemblyincludes an annular case and a front acoustic panel coupled to theannular case to dampen vibrations produced by the fan blades duringoperation of the gas turbine engine;

FIG. 2 is an enlarged view of a portion of the fan case assembly of FIG.1 with portions exploded away showing that the fan case assembly furtherincludes a bolting arrangement including a first captured nut arrangedto lie within a cavity defined by the acoustic panel and a firstattachment that extends radially through the annular case and into thecavity defined by the acoustic panel from radially outside the gasturbine engine to facilitate installation of the acoustic panel on theannular case and removal of the acoustic panel from the annular case forservice or replacement;

FIG. 3 is a cross-sectional view of the fan case assembly showing thatthe acoustic panel includes a panel body, a forward support bracket thatdefines the cavity at a forward end of the panel body, and an aftsupport bracket that defines a second cavity at an aft end of the panelbody and that is configured to receive a second captured nut and asecond attachment fastener that extends through the annular case andinto the second cavity to retain the aft end of the acoustic panel tothe annular case;

FIG. 4 is an exploded assembly view of the acoustic panel from FIG. 3showing that the panel body includes a panel core and inner and outerskins coupled to the forward and aft support brackets to locate theforward and aft support brackets radially between the inner and outerskins and axially forward of and aft of the panel core, respectively;

FIG. 5 is a cross-sectional view of the acoustic panel showing that theacoustic panel further includes an adhesive assembly configured to joinportions of the panel body and the forward and aft support brackets toone another to form a composite acoustic panel assembly that forms theacoustic panel shown in FIGS. 2-4 ;

FIG. 6 is cross sectional view of a second acoustic panel that can beused with the gas turbine engine shown in FIG. 1 ;

FIG. 7 is cross sectional view of a third acoustic panel that can beused with the gas turbine engine shown in FIG. 1 ;

FIG. 8 is cross sectional view of a fourth acoustic panel that can beused with the gas turbine engine shown in FIG. 1 ; and

FIG. 9 is cross sectional view of another acoustic panel and anotherannular case that can be used with the gas turbine engine shown in FIG.1 .

DETAILED DESCRIPTION OF THE DRAWINGS

For the purposes of promoting an understanding of the principles of thedisclosure, reference will now be made to a number of illustrativeembodiments illustrated in the drawings and specific language will beused to describe the same.

A gas turbine engine 10 in accordance with the present disclosure isshown in FIG. 1 and includes an engine core 12 and a fan 14 arrangedupstream of the engine core 12. The engine core 12 is configured tocompress and combust air entering the gas turbine engine 10 to driverotation of one or more shafts 16 about a rotation axis 18 of the gasturbine engine 10. The one or more shafts 16 interconnect the enginecore 12 and the fan 14 to cause rotation of the fan 14 and to providethrust for the gas turbine engine 10.

The engine core 12 includes a compressor 20, a combustor 22, and aturbine 24. The compressor 20 includes one or more stages of rotatingblades that compress air entering the engine core 12 and producepressurized air which is transferred downstream to the combustor 22. Thecombustor is configured to mix fuel with the pressurized air and combustthe fuel and pressurized air to produce combustion products which aretransferred downstream to the turbine 24. The turbine 24 also includesone or more stages of rotating blades which are coupled to the one ormore shafts 16 and are driven in rotation about the axis 18. Rotation ofthe one or more shafts 16 causes rotating components of the fan 14 torotate about the axis 18.

The fan 14 includes a fan case assembly 26 extending circumferentiallyaround the axis 18 and a plurality of rotating blades 28 spaced radiallyinward of the fan case assembly 26 as shown in FIG. 1 . The fan caseassembly 26 provides an outer boundary of a flowpath 30 into the gasturbine engine 10 and is arranged to lie adjacent the plurality ofrotating blades 28. The plurality of rotating blades 28 are coupled toat least one of the one or more shafts 16 for rotation therewith aboutthe axis 18. During operation, radial tips of the plurality of rotatingblades 28 interface with portions of the fan case assembly 26.Interaction between the fan case assembly 26 and the radial tips of theplurality of rotating blades 28 is configured to minimize pressurelosses and increase efficiencies of the gas turbine engine 10.

The fan case assembly 26 is fixed relative to the plurality of blades 28and includes an annular case 32, a front acoustic panel 34 supported bythe annular case 32, and a bolting arrangement 36 configured to securethe acoustic panel 34 to the annular case 32 as shown in FIG. 2 . Theannular case 32 extends circumferentially about the axis 18 of the gasturbine engine 10. The acoustic panel 34 also extends circumferentiallyaround the axis 18 and may form a full hoop or a plurality ofcircumferentially spaced segments at or near radial tips of theplurality of blades 28. The acoustic panel 34 is located radially inwardof at least a portion of the annular case 32 and is offset axiallyforward of the plurality of blades 28 at an inlet end of the gas turbineengine 10. In some embodiments, the acoustic panel 34 is a rear acousticpanel that is mounted to the annular case and located axially aft of theplurality of blades 28. The bolting arrangement 36 couples the acousticpanel 34 to the annular case 32 in a way that facilitates assembly ofthe fan case assembly 26 while minimizing obstructions in the flowpath30.

The annular case 32 has an inner radial surface 38 and an outer radialsurface 40 opposite the inner radial surface 38 and facing away from theaxis 18 as shown in FIGS. 2 and 3 . The annular case 32 is formed toinclude at least one aperture or passageway 42 that extends all the waythrough the annular case 32 from the outer radial surface 40 to theinner radial surface 38. The annular case 32 may be formed to include achannel 35 that opens and faces toward axis 18. The acoustic panel 34 isarranged to lie within the channel 35 and is retained in the channel 35by the bolting arrangement 36.

The bolting arrangement 36 includes at least one captured nut 44 (alsocalled a retainer) coupled to the acoustic panel 34 and at least onecorresponding attachment fastener 46 coupled to the annular case 32 asshown in FIGS. 2 and 3 . The captured nut 44 is fixed to the acousticpanel 34 and is configured to receive the attachment fastener 46. Theattachment fastener 46 extends through the aperture 42 from outside theflowpath 30 and is received in the captured nut 44 to secure theacoustic panel 34 to the annular case 32.

The acoustic panel 34 is configured to dampen noise and vibrationscaused by the plurality of blades 28 or other parts of the gas turbineengine 10. The acoustic panel 34 includes a panel body 48 and one ormore support brackets 52 coupled to the panel body 48 as shown in FIGS.3 and 4 . The panel body 48 is at least partially formed from analuminum honeycomb material and is positioned radially inward of theannular case 32 to partially define the flowpath 30. The support bracket52 is coupled to an axially-forward and/or axial aft end of the panelbody 48 and supports the captured nut 44 relative to the panel body 48for receipt of the attachment fastener 46. The support bracket 52 alsoincrease rigidity of the acoustic panel 34 to increase support providedby the bolting arrangement 36.

The panel body 48 includes an inner body section 49 and an outer bodysection 51 as shown in FIG. 3 . The inner body section 49 has a firstaxial length 53 and the outer body section 51 has a second axial length55 that is less than the first axial length 53. The at least one supportbracket 52 includes or provides a flange 76 that is coupled to the outerbody section 51 and extends in an axial direction away from the outerbody section 51. The flange 76 is spaced apart from the inner bodysection 49 to provide a cavity 56 radially between the flange 76 and theinner body section 49. The captured nut 44 is coupled to a radiallyintermediate surface 77 of the flange 76 and is arranged to lie in thecavity 56 to locate the captured nut 44 between the flange 76 and theinner body section 49 and to locate the inner body section 49 betweenthe captured nut 44 and the flowpath 30.

In some embodiments, the attachment flange 76 has a first radialthickness 120 and the inner body section 49 has a second radialthickness 122 greater than the first radial thickness 120 as shown inFIG. 3 . The outer body section 51 may have a third radial thickness 124greater than the first radial thickness 120 and equal to or less thanthe second radial thickness 122. The inner body section 49 may be formedwithout any attachment through holes such that no fasteners (i.e.attachment fastener 46) extend through the inner body section 49. Theouter body section 51 may be formed without any through holes such thatno fasteners (i.e. attachment fastener 46) extend into the outer bodysection 51.

In the illustrative embodiment, the acoustic panel 34 includes bothforward and aft support brackets 52, 54 that each receive correspondingcaptured nuts 44, 45 and attachment fasteners 46, 47 as shown in FIGS.2-4 . Each support bracket 52, 54 at least partially defines a cavity56, 58 that is spaced apart from the flowpath 30. The cavities 56, 58are located radially between a radially outer surface 60 of the panelbody 48 and a radially inner surface 62 of the panel body 48. Allportions of the captured nuts 44, 45 and the attachment fasteners 46, 47are spaced apart from the flowpath 30 and the radially inner surface 62of the panel body 48. No portions of the captured nuts 44, 45 and theattachment fasteners 46, 47 protrude into or define the flowpath 30. Theradially inner surface 62 of the panel body 48 may be aligned withflowpath surfaces of the annular case 32 to provide a continuousflowpath surface defining the flowpath 30. One or more seals or fillermaterial may be located axially between the acoustic panel 34 and theannular case 32 to fill any gaps therebetween.

In some embodiments, all or portions of the acoustic panel 34 may bemade from a plurality of separate components that are adhered togetherto form a composite acoustic panel 34 as suggested in FIGS. 4 and 5 .The panel body 48 may include a panel core 66 and laminates or a corecover having a radially outer skin 68 coupled to an outer surface of thepanel core 66 and a radially inner skin 70 coupled to an inner surfaceof the panel core 66. The panel core 66 may be made from an aluminumhoneycomb material that dampens vibrations produced by the plurality ofblades 28 during operation of the gas turbine engine 10. The aluminumhoneycomb material includes a plurality of hexagonally-shaped cells orother polygon-shaped cells (i.e. Flex-Core® shaped) that define voids inthe panel core 66. The radially inner skin 70 may have holes orapertures drilled, machined, and/or formed to extend radially throughthe inner skin 70 to expose portions of the panel core 66 and increasevibration dampening capabilities of the acoustic panel 34. The innermost portions 83 of the brackets 52, 54 may also include perforations.

The radially outer skin 68 and the radially inner skin 70 each have alength that is greater than the outer body section 51 and partiallycouple to both the forward support bracket 52 and the aft supportbracket 54. In some embodiments, forward and/or aft portions of theskins 68, 70 provide part of the forward and/or aft support bracket 52,54 to form flanges 76. In some embodiments the radially inner skin 70has a greater radial thickness than the radially outer skin 68 toprovide greater durability on the flowpath side of the acoustic panel34.

The radially outer skin 68 and the radially inner skin 70 may eachinclude a glass-reinforced polymer ply or layer that increases strengthand stiffness of the acoustic panel 34. The plurality ofglass-reinforced polymer plies or layers are stacked radially on top ofone another. The plurality of glass-reinforced layers may be adhered tothe forward and/or aft support brackets 52, 54 to form the flanges 76with the support brackets 52, 54. In the illustrative embodiment, eachsupport bracket 52, 54 is made from one or more glass-reinforced polymerplies or layers. In other embodiments, another suitable material may beused to form the support brackets 52, 54 such as a carbon-reinforcedpolymer, for example. In other embodiments, another suitable materialmay be used to form radially outer and inner skins 68, 70 and thesupport brackets 52, 54 such as a carbon-reinforced polymer and highmodulus polypropylene, for example.

The forward support bracket 52 is coupled to a forward end of the panelcore 66 and is arranged to lie radially between the radially outer skin68 and the radially inner skin 70. The forward support bracket 52 atleast partially defines the cavity 56 radially between the radiallyouter skin 68 and the radially inner skin 70. The cavity 56 is locatedaxially forward of the panel core 66 and is open in a forward orupstream direction to receive the captured nut 44 during assembly.

The aft support bracket 54 is similarly shaped compared to the forwardsupport bracket 52 except that the second cavity 58 defined by the aftsupport bracket 54 opens in a rearward or downstream direction oppositethe first cavity 56. Accordingly, only the forward support bracket 52 isdescribed below and the disclosure of the forward support bracket 52 isincorporated by reference for the aft support bracket 54. Similarreference numbers are used to reference common features between theforward support bracket 52 and the aft support bracket 54.

The forward support bracket 52 includes an attachment flange 76 coupledthe outer body section 51 and a panel-body support 78 coupled to theinner body section 49 as shown in FIGS. 3 and 4 . The attachment flange76 is coupled to an outer end of the outer body section 51 and has aradially intermediate surface 77 that faces toward at least a portion ofthe panel-body support 78. The captured nut 44 is mounted directly onthe radially intermediate surface 77 of the attachment flange 76. Insome embodiments, the attachment flange 76 also includes portions of theradially outer skin 68. The panel-body support 78 may be coupled to theattachment flange 76 directly or indirectly and is coupled to the innerbody section 49 to transfer loads from the panel body 48 to theattachment flange 76 and the bolting arrangement 36.

The attachment flange 76 extends axially away from the outer bodysection 51 and has the radially intermediate surface 77. The attachmentflange 76 may be coupled to the radially outer skin 68. Alternatively,the radially outer skin 68 may stop short of the attachment flange 76such that the attachment flange 76 alone supports the acoustic panel 34on the annular case 32. The outer skin 68 may be spaced apart from theannular case 32 and the support brackets 52, 54 may be sized to providea gap between the outer skin 68 and the annular case 32.

The panel-body support 78 includes an outer radially extending strip 80coupled to the attachment flange 76, an outer axially-extending strip81, an inner axially-extending strip 83, and an inner radially-extendingstrip 85 interconnecting the outer and inner axially extending strips81, 83 as shown in FIGS. 3 and 4 . The outer radially-extending strip 80is coupled to the outer body section 51 and extends between andinterconnects the attachment flange 76 and the outer axially-extendingstrip 81. The outer and inner axially-extending strips 81, 83 are spacedradially from one another to locate a portion of the inner body section49 radially there between. The inner radially-extending strip 85 isarranged at an axial end of the inner body section 49 and extendsradially between axial ends of the outer and inner axially-extendingstrips 81, 83. The attachment flange 76 is arranged radially outward ofthe outer axially-extending strip 81 of the panel-body support 78 todefine the cavity 56, 58 radially between the attachment flange 76 andthe outer axially-extending strip 81.

The panel core 66 may be formed to include a cutout 87 in an radiallyinner end of the inner body section 49 as shown in FIGS. 3 and 4 . Theinner axially-extending strip 83 is sized to fit in the cutout 87 suchthat the inner axially-extending strip 83 is flush with a radially innersurface of the panel core 66. The radially inner skin 70 may then beattached to the inner axially extending-strip 83 and the panel core 66.In some embodiments, inner axially-extending strip 83 and the cutouts 87may be omitted.

The attachment flange 76 is formed or machined later to include anaperture 82 or passageway that is aligned with aperture 42 in annularcase 32. The captured nuts 44, 45 are coupled to a correspondingattachment flange 76 and are aligned with a corresponding aperture 82 toreceive a corresponding attachment fastener 46, 47 passing throughapertures 42, 82 to secure the acoustic panel 34 to the annular case 32.The radially outer skin 68 may at least partially overlie the attachmentflange 76 to reinforce the forward and/or aft support bracket 52, 54 andmay be formed or machined to include an aperture 84 that is aligned withthe aperture 82 formed in the attachment flange 76 when fully assembled.

The captured nuts 44, 45 are each fixed to a radially inner surface ofeach corresponding attachment flange 76 as shown in FIGS. 3 and 4 . Inthe illustrative embodiment, each captured nut 44, 45 is a riveted nutplate that is coupled to the corresponding attachment flange 76 byfasteners or adhesives to at least temporarily retain the captured nut44, 45 in place prior to receiving the attachment fastener 46, 47. Eachattachment fastener 46, 47 may be a bolt or another similar fastenerhaving a length sufficient to reach the captured nut 44, 45 fromradially outward of the annular case 32. Each captured nut 44, 45 andattachment fastener 46, 47 has complementary threads that interlock whenfully assembled to secure the acoustic panel 34 to the annular case 32.

The acoustic panel 34 further includes a plurality of adhesive layersthat join the panel body 48 to the forward and aft support brackets 52,54 as shown in FIG. 5 . Each of the adhesive layers are shown withexaggerated thicknesses in FIG. 5 to illustrate their location inacoustic panel 34, but it should be appreciated that the thicknesses ofeach adhesive layer may vary relative to one another and relative toeach component of the panel body 48 and the support brackets 52, 54.

The attachment flange 76 of the support brackets 52, 54 are bonded tothe radially outer skin 68 by a first supported adhesive layer 90 asshown in FIG. 5 . The panel-body support 78 of the support brackets 52,54 are bonded to the radially inner skin 70 by a second supportedadhesive 92. Loads acting on the acoustic panel 34 are transferred fromthe radially inner skin 70, through the support brackets 52, 54 to theradially outer skin 68 and the bolting arrangement 36 due to the supportbrackets 52, 54 being bonded to the radially outer and inner skins 68,70. The first and second supported adhesive layers 90, 92 include acarrier and an adhesive resin infused around the carrier. The supportedadhesive layers 90, 92 are a medium weight supported film adhesive inthe illustrative embodiment, however, in other embodiments, other typesof adhesives can be used.

The panel core 66 is bonded to the radially outer skin 68 by a firstlayer of unsupported adhesive 94 and to the radially inner skin 70 by asecond layer of unsupported adhesive 96 as shown in FIG. 5 . Eachunsupported adhesive 94, 96 is may be reticulated or non-reticulated andincludes and/or consists of an adhesive resin. The unsupported adhesivelayers 94, 96 may also bond the panel core 66 to the inneraxially-extending strip 83 of each support bracket 52, 54.

Each support bracket 52, 54 is bonded to the panel core 66 by a layer offoamed adhesive 98, 100 as shown in FIG. 5 . Each layer of foamedadhesive 98, 100 is arranged to lie axially between the panel core 66and the corresponding support bracket 52, 54. The foamed adhesive 98,100 is configured to expand upon curing and is configured to extend intoand fill voids in the panel core 66 to minimize air gaps between thesupport brackets 52, 54 and the panel core 66. The foamed adhesive 98,100 may be a foaming film adhesive or an epoxy foaming filler, forexample.

In some embodiments, the fan case assembly 26 may further include a seal104 positioned axially between an aft end of the acoustic panel 34 andthe annular case 32 as shown in FIG. 3 . In the illustrative embodiment,the seal 104 is a flap seas that are coupled to the acoustic panel 34and are self-biasing into engagement with annular case 32 to sealbetween the acoustic panel 34 and the annular case 32 near the flowpath30. Another similar seal may be included between a forward end of theacoustic panel 34 and the annular case 32 if a portion of the annularcase 32 lies in front of the acoustic panel 34 (such as for a rearpanel). Other types of seals may also be used in place of the flap seal104 such as a rope seal or a bulb seal.

Another embodiment of an acoustic panel 234 is shown in FIG. 6 . Theacoustic panel 234 is substantially similar to the acoustic panel 34 ofFIGS. 1-5 . Similar reference numbers are used to describe similarfeatures that are common between acoustic panel 234 and acoustic panel34. The disclosure of acoustic panel 34 is incorporated by referenceherein for acoustic panel 234 except for the differences discussedbelow.

The acoustic panel 234 includes a panel body 248 and forward and aftsupport brackets 252, 254 that each include an attachment flange 276 anda panel-body support 278 as shown in FIG. 6 . Each panel-body support278 includes an outer radially extending strip 280, an outeraxially-extending strip 281, and an inner radially-extending strip 285.Thus, the panel-body support 278 does not include an inneraxially-extending strip.

The acoustic panel further includes a panel core 266, a radially outerskin 268, and a radially inner skin 270 as shown in FIG. 6 . A pluralityof adhesive layers bond each part of the acoustic panel together to forma composite acoustic panel 234. A first layer of supported adhesive 90is positioned between the radially outer skin 268 and the attachmentflanges 276. A first layer of unsupported adhesive 94 is positionedbetween the radially outer skin 268 and the panel core 266. A secondlayer of unsupported adhesive 96 is positioned between the radiallyinner skin 270 and the panel core 266. Layers of foamed adhesive 98, 100are positioned between support brackets 252, 254 and the panel core 266.

Another embodiment of an acoustic panel 334 is shown in FIG. 7 . Theacoustic panel 334 is substantially similar to the acoustic panel 34 ofFIGS. 1-5 . Similar reference numbers are used to describe similarfeatures that are common between acoustic panel 334 and acoustic panel34. The disclosure of acoustic panel 34 is incorporated by referenceherein for acoustic panel 334 except for the differences discussedbelow.

The acoustic panel 334 includes a panel body 348 and forward and aftsupport brackets 352, 354 that each include an attachment flange 376 anda panel-body support 378 as shown in FIG. 7 . Each attachment flange 376and panel-body support 378 are formed as separate components that areadhered together.

Each panel-body support 378 includes an outer axially-extending strip381, a radially-extending strip 385, and an inner axially-extendingstrip 383. Thus, the panel-body support 378 does not include an outerradially-extending strip. Each attachment flange 376 includes an outeraxially-extending strip 391, a radially-extending strip 393, and aninner axially-extending strip 395. The attachment flange 376 may bepre-cured prior to being assembled with the rest of the acoustic panel334. The panel-body support 378 may be co-cured with the acoustic panel334 after the acoustic panel 334 is assembled.

The acoustic panel further includes a panel core 366, a radially outerskin 368 coupled to the outer axially-extending strip 391, and aradially inner skin 370 coupled to inner axially-extending strip 383 asshown in FIG. 7 . A plurality of adhesive layers bond each part of theacoustic panel together to form a composite acoustic panel 334. A firstlayer of supported adhesive 90 is positioned between the radially outerskin 368 and the attachment flanges 376. A first layer of unsupportedadhesive 94 is positioned between the radially outer skin 368 and thepanel core 366. A second layer of unsupported adhesive 96 is positionedbetween the radially inner skin 370 and the panel core 366. Layers offoamed adhesive 98, 100 are positioned between support brackets 352, 354and the panel core 366. The outer axially-extending strip 381 of thepanel-body support 378 is bonded to the inner axially-extending strip395 by a layer of unsupported adhesive 397 positioned radially therebetween. Optionally, a layer of unsupported adhesive may be placedradially between the panel core 366 and the outer axially-extendingstrip 381 in place of foaming adhesive 98, 100. This may minimize anamount of adhesive material that flows into the cells of the panel core366 thereby maximizing acoustic dampening capabilities of the acousticpanel 334.

Another embodiment of an acoustic panel 434 is shown in FIG. 8 . Theacoustic panel 434 is substantially similar to the acoustic panel 34 ofFIGS. 1-5 . Similar reference numbers are used to describe similarfeatures that are common between acoustic panel 434 and acoustic panel34. The disclosure of acoustic panel 34 is incorporated by referenceherein for acoustic panel 434 except for the differences discussedbelow.

The acoustic panel 434 includes a panel body 448 and forward and aftsupport brackets 452, 454 that each include an attachment flange 476 anda panel-body support 478 as shown in FIG. 8 . Each attachment flange 476and panel-body support 478 are formed as separate components that areadhered together.

Each panel-body support 478 includes an outer radially-extending strip480, an outer axially-extending strip 481, an inner radially-extendingstrip 485, and an inner axially-extending strip 483. Each attachmentflange 476 includes an axially-extending strip 491 and aradially-extending strip 493 coupled to the outer radially-extendingstrip 480. The attachment flange 476 may be pre-cured prior to beingassembled with the rest of the acoustic panel 434. The panel-bodysupport 478 may be co-cured with the acoustic panel 434 after theacoustic panel 434 is assembled.

The acoustic panel further includes a panel core 466, a radially outerskin 468 coupled to the axially-extending strip 491, and a radiallyinner skin 470 coupled to inner axially-extending strip 483 as shown inFIG. 8 . A plurality of adhesive layers bond each part of the acousticpanel together to form a composite acoustic panel 434. A first layer ofsupported adhesive 90 is positioned between the radially outer skin 468and the attachment flanges 476. A second layer of supported adhesive 92is positioned between the radially inner skin 470 and the attachmentflanges 476. A first layer of unsupported adhesive 94 is positionedbetween the radially outer skin 468 and the panel core 466. A secondlayer of unsupported adhesive 96 is positioned between the radiallyinner skin 470 and the panel core 466. Layers of foamed adhesive 98, 100are positioned between support brackets 452, 454 and the panel core 466.Radially-extending strip 493 of the attachment flange 476 is bonded tothe outer radially-extending strip 480 of the panel-body support 478 bya layer of unsupported adhesive 497. Optionally, a layer of unsupportedadhesive may be placed radially between the panel core 366 and the inneraxially-extending strip 483 in place of foaming adhesive 98, 100. Thismay minimize an amount of adhesive material that flows into the cells ofthe panel core 466 thereby maximizing acoustic dampening capabilities ofthe acoustic panel 434.

Another embodiment of a fan case assembly 526 is shown in FIG. 9 . Thefan case assembly 526 is substantially similar to the fan case assembly26 of FIGS. 1-5 . Similar reference numbers are used to describe similarfeatures that are common between fan case assembly 526 and fan caseassembly 26. The disclosure of fan case assembly 26 is incorporated byreference herein for fan case assembly 526 except for the differencesdiscussed below.

Fan case assembly 526 includes an annular case 532, an acoustic panel534, and a bolting arrangement 536 as shown in FIG. 9 . The annular case532 is formed to include a channel 535 opening toward axis 18. Theacoustic panel 534 is arranged to lie within the channel 535 and issecured to the annular case 532 by the bolting arrangement 536 insubstantially the same manner described above with fan case assembly 26.

The annular case 532 includes an axially-extending flange 537 thatextend axially forward from a portion of the annular case 532 definingthe channel 535 as shown in FIG. 9 . The acoustic panel 534 includes apanel body 548 and a forward support bracket 552. The forward supportbracket 552 is arranged to lie at an opposite end of the channel 535 tothe flange 537 such that a cavity 556 is defined radially by only theforward support bracket 552. An aft end 539 of the panel body 548 issupported radially by the flange 537 and is not retained to the annularcase by the bolting arrangement 536. In this way, the acoustic panel 534includes only the forward support bracket 552 and the boltingarrangement 536 is installed only at the forward end of the acousticpanel 534. An o-ring seal 504 may be coupled to the flange 537 andengage the aft end 539 of the acoustic panel 534 to support the panel534. A similar arrangement may be provided between the forward end ofthe acoustic panel 534 and annular case 532 such that the acoustic panelincludes only an aft support bracket, such as for a rear panel.

The acoustic panel 34 of the present disclosure is divided into aplurality of segments that combine to form a continuous, full-hoop panelforward the plurality of blades 28.

In some embodiments, the present disclosure includes an acoustic panelwith flanges at the fore and aft of the outer skin to attach and holdriveted captured nuts. This arrangement may allow for bolting from theouter surface of the fan case and may permit the entire inner surface ofthe front acoustic panel (FAP) to be acoustically treated while alsoallowing the panel to be formed without any filler material for boltholes, for example.

In some embodiments, a front end of the fan may include a flange thatcovers and hides the captured nut and pocket. This would maintainacoustic treatment while avoiding aerodynamic interruptions. The panelmay include sufficient honeycomb depth between the pocket and theflowpath surface. In some embodiments, the panel's aft end may besecured by the bolting arrangement as well to avoid a lip and o-ringconfiguration of the annular case as shown in FIG. 9 . A flap seal couldbe used between liners as well thereby reducing or eliminating radialflow between panels but reducing assembly cost and time for assembly.The present disclosure may provide greater serviceability options toeasily remove and replace panels and may be easier to service thanpanels with filled access holes on the flowpath surface, for example.

In some embodiments, the panels may be used in a composite case withlimited hole counts as these cases may not include hangers or otherfeatures to use to secure acoustic panels. The front acoustic panels maybe relatively short (i.e. 4″ to 6″ long axially), so that it may not benecessary to attach the bolts at the forward most or aft most extreme ofthe panel to meet dynamics requirements. This would provide axial spacebetween the bolting arrangement to the front flange or casing hookfillet of the case. The inner portion of the panel with honeycombmaterial may extend outward toward the annular case and may provide aseal against radial air flows.

In some embodiments, attaching the panels at their outer end reduces oreliminates interruptions to the flowpath and the need to fill any boltholes on the flowpath side of the panel after panel installation. Thepresent disclosure may allow the panels to be formed without pottedinserts which could have a concern around torque capability.Additionally, the present disclosure allows portions of the panelradially inward of the bolting arrangement remain intact and not includeany holes for attachment purposes. Holes that extend through the paneland are exposed on the flowpath side of the panel may reduce theattenuation overall and may add manufacturing complexity and cost. Thepanels of the illustrative embodiment include a uniform perforationinner skin and riveted captured nuts on the inside of the outer skinwithin the pocket(s). This may maximize acoustic treatment, visualappearance, and may provide a lightweight panel.

In some engines, there are fasteners that pass through the innerflowpath just ahead of the fan in the FAP are filled over with fillermaterial. This requires a longer assembly process including: torqueingthe bolt (which has undesirable oil lubricant), cleaning the hole,installing a foam cap, and then using a putty knife to fill the holewith a suitable filler material. The filler material could potentiallycause flow disruptions if not smooth and may clog perforation holes ifnot properly masked. The filler material may be visually un-appealingand may lead to longer turn-around time between cleaning, masking,prepping, filling, and curing. The present disclosure avoids most or allof these issues and steps.

In some embodiments, the front and aft end of the panel may bereinforced to connect the outer skin to the inner skin. In someembodiments, compression sheet molding compound rails or laid uppre-preg ones may be used to reinforce the forward and/or aft end of thepanel. Laid up pre-preg may be stronger and lighter weight but may bemore labor intensive. In some embodiments, one end of the panel may bereinforced and attached from the outside using the bolting arrangementwhile the other end rests its lip on an o-ring or seal on the flange ofthe annular case. In some embodiments, the attachment provided by thebolting arrangement may retrofit into existing panel configurationsusing bolting through panels.

While the disclosure has been illustrated and described in detail in theforegoing drawings and description, the same is to be considered asexemplary and not restrictive in character, it being understood thatonly illustrative embodiments thereof have been shown and described andthat all changes and modifications that come within the spirit of thedisclosure are desired to be protected.

What is claimed is:
 1. An acoustic panel for a gas turbine engine, theacoustic panel comprising a panel body including an outer body sectionhaving a first axial length and an inner body section having a secondaxial length greater than the first axial length, a panel-body coverincluding a radially outer skin coupled to the outer body section of thepanel body and a radially inner skin coupled to the inner body sectionof the panel body, and a forward support bracket coupled to the panelbody and arranged radially between the radially outer skin and theradially inner skin, the forward support bracket including an attachmentflange that extends axially forward away from the outer body section anda panel-body support coupled to the inner body section of the panel bodyand at least partially spaced apart from the attachment flange toprovide a radial cavity between the attachment flange and the panel-bodysupport.
 2. The acoustic panel of claim 1, wherein the panel-bodysupport includes an outer radially-extending strip coupled to the outerbody section and the attachment flange, an outer axially-extending stripcoupled to the inner body section, an inner radially-extending stripcoupled to the inner body section.
 3. The acoustic panel of claim 2,wherein the panel-body support further includes an inneraxially-extending strip located radially between the inner body sectionand the radially inner skin.
 4. The acoustic panel of claim 3, whereinthe inner body section is formed to include a cutout and the inneraxially-extending strip is located in the cutout.
 5. The acoustic panelof claim 2, wherein the radial cavity is defined by the attachmentflange, the outer axially-extending strip and the outerradially-extending strip, and wherein the radial cavity opens axiallyaway from the panel body.
 6. The acoustic panel of claim 1, wherein theattachment flange includes an outer axially-extending strip coupled tothe radially outer skin and a radially-extending strip coupled to atleast one of the inner body section and the panel-body support.
 7. Theacoustic panel of claim 6, wherein the attachment flange is made from afirst glass-reinforced polymer material and the panel-body support ismade from a second glass-reinforced polymer material different than thefirst glass-reinforced polymer material.
 8. The acoustic panel of claim6, wherein the attachment flange further includes an inner axiallyextending strip spaced radially from the outer axially-extending stripand that is coupled to the panel-body support and partially defines thecavity radially between the outer axially-extending strip and the inneraxially-extending strip.
 9. The acoustic panel of claim 1, wherein thepanel body includes an aluminum honeycomb material, and wherein theradially outer skin, the radially inner skin, and the forward supportbracket each include a glass-reinforced polymer.
 10. The acoustic panelof claim 9, wherein the forward support bracket is bonded to theradially outer skin by a first supported adhesive layer and forwardsupport bracket is bonded to the radially inner skin by a secondsupported adhesive such that loads are transferred from the radiallyinner skin, through forward support bracket, and to the radially outerskin.
 11. The acoustic panel of claim 10, wherein a layer of unsupportedadhesive is arranged to lie between the panel core and the radiallyouter skin and between the panel core and the radially inner skin. 12.The acoustic panel of claim 9, wherein a layer of foamed adhesive isarranged to lie axially between the panel core and the forward supportbracket.
 13. The acoustic panel of claim 1, wherein the acoustic panelfurther includes an aft support bracket coupled to an aft end of thepanel core and arranged to lie radially between the radially outer skinand the radially inner skin, the aft support bracket defines a secondcavity radially between the radially outer skin and the radially innerskin and located axially aft of the panel core.
 14. An acoustic panelfor a gas turbine engine, the acoustic panel comprising a panel bodyincluding an outer body section and an inner body section, and a supportbracket coupled to the panel body, the support bracket including anattachment flange that extends axially forward away from the outer bodysection and a panel-body support coupled to the inner body section ofthe panel body and at least partially spaced apart from the attachmentflange to provide a radial cavity located between the attachment flangeand the panel-body support and located radially outward of the innerbody section.
 15. The acoustic panel of claim 14, further comprising apanel-body cover including a radially outer skin coupled to the outerbody section of the panel body and a radially inner skin coupled to theinner body section of the panel body to locate the support bracketradially between the radially outer skin and the radially inner skin.16. The acoustic panel of claim 14, wherein the panel-body supportincludes an outer radially-extending strip coupled to the outer bodysection and the attachment flange, an outer axially-extending stripcoupled to the inner body section, and an inner radially-extending stripcoupled to the inner body section.
 17. The acoustic panel of claim 14,wherein the panel-body support further includes an inneraxially-extending strip coupled to a radially inner surface of the innerbody section.
 18. The acoustic panel of claim 14, wherein the attachmentflange includes an outer axially-extending strip and aradially-extending strip coupled to at least one of the inner bodysection and the panel-body support.
 19. The acoustic panel of claim 18,wherein the attachment flange further includes an inner axiallyextending strip spaced radially from the outer axially-extending stripand that is coupled to the panel-body support and partially defines thecavity radially between the outer axially-extending strip and the inneraxially-extending strip.
 20. The acoustic panel of claim 14, wherein thepanel body includes an aluminum honeycomb material, and wherein thesupport bracket includes a glass-reinforced polymer, and wherein a layerof foamed adhesive is arranged to lie axially between the panel core andthe support bracket.